In the production of electric motors in large unit quantities for hybrid vehicles, the installation, in particular the fixing, of the permanent magnets in the rotor represents a relatively great cost factor.
Use is very commonly made of adhesive bonding techniques, which necessitate cumbersome techniques during the installation process and in particular during a recycling process, for example during the separation of the permanent magnets from the rotor components. Such adhesive bonding techniques are known for example from DE 202 01 831.
Alternative methods provide clamping, for example by suitable clamping elements composed of plastic, or calking of the permanent magnets in a groove provided for them. Although such methods facilitate the recycling process, they are often difficult to implement in the installation process due to a lack of flexibility, because relatively large tolerances must be bridged. Technological background is thus known for example from DE 102 53 950 A1, DE 10 2005 041 676 A1, EP 2 436 100 B1, DE 10 2005 048 731 A1, EP 2 437 377 A1, DE 10 2012 016 927 A1 and EP 2 249 460 B1. In part, due to relatively weak interference fits, other methods under some circumstances do not provide adequate security against the permanent magnets loosening and falling out at high rotational speeds and under high vibration loads, such as may arise for example in the case of belt-type and crankshaft starter generators.
Furthermore, DE 10 2005 002 332 A1 has disclosed a rotor for a permanently excited electric machine which is suitable for use in an electric drive motor of a vehicle. Here, magnets are held in grooves of the rotor by interference fits. It is proposed that, in the region of the grooves, at least one recess adjacent to the groove be arranged at at least one point. It is sought thereby to achieve that the material in the region of the walls of the groove has a certain elasticity due to the recess arranged in the material. Such a recess corresponds in principle to a flexible beam clamped on both sides, which however under some circumstances exhibits a lack of flexibility insufficient to ensure easy and destruction-free or damage-free installation of the permanent magnets.